Battery electric vehicles (BEVs) may be caused to move by operation of an electric machine. Plug-in hybrid electric vehicles (PHEVs) may be caused to move by operation of an electric machine and/or an internal combustion engine. The electric machine, in either case, may receive electrical power from an on-board battery. The battery may include a plurality of cells electrically connected in series and be charged with electrical power from a utility grid or other source, etc.
For efficiency and battery durability reasons, it may be desirable to keep the states of charge/energy contents of the battery cells approximately equal. Providing energy to or removing energy from the battery, however, may cause the states of charge/energy contents of the battery cells to become unequal.